The present invention relates to a laser survey instrument, by which it is possible to form a measurement plane, in particular an arbitrary tilt setting plane tilted by a given angle with respect to a horizontal reference plane in addition to a horizontal reference plane, by using a laser beam.
In order to obtain a horizontal reference level for wide range, a laser survey instrument is used to replace an optical leveling device.
By the laser survey instrument, it is possible to easily obtain a horizontal reference plane by rotary irradiation of a laser beam in a horizontal direction and to obtain a horizontal reference line by irradiating a laser beam to wall or the like, and the instrument of this type has been widely used as the means to obtain a reference level.
As the laser beam to be irradiated, both visible light and invisible light are used. When visible light is used, visibility is inferior under sunlight, and it is mostly used for indoor applications such as positioning of window frame or ceiling assembly during construction or reconstruction of a building. When invisible light is used, photoelectric conversion photodetector is employed on light receiving side, and the laser survey instrument can be used for both indoor and outdoor applications. In outdoor applications, it is used to form a reference plane for foundation of building or for ground leveling work.
In recent years, tilted ceilings are designed in many new buildings and a tilted reference plane or a tilted reference line are required for setting-out operation, for example, to mount indoor light to suit the ceiling surface or the work to install handrail along staircase.
However, the conventional type laser survey instrument as described above is primarily designed to form a horizontal reference plane or a horizontal reference line, and a tilted reference plane or a tilted reference line cannot be easily formed. For this reason, the conventional type instrument is not suitable for outdoor work or indoor interior work of a building having tilted portion. It is not possible to provide high working accuracy in mounting indoor light to suit the ceiling surface or in installing handrail along staircase as described above, and there are strong demands on the laser survey instrument, by which it is possible to easily perform tilt setting and to obtain a tilted reference plane and a tilted reference line.